// krazy:excludeall=copyright (email of Maxim is missing)
/*
    This file is a part of the KDE project

    SPDX-FileCopyrightText: 2006 Zack Rusin <zack@kde.org>
    SPDX-FileCopyrightText: 2006-2007, 2008 Fredrik Höglund <fredrik@kde.org>

    The stack blur algorithm was invented by Mario Klingemann <mario@quasimondo.com>

    This implementation is based on the version in Anti-Grain Geometry Version 2.4,
    SPDX-FileCopyrightText: 2002-2005 Maxim Shemanarev <http://www.antigrain.com>

    SPDX-License-Identifier: BSD-2-Clause
*/

#include "imagefilter_p.h"

#include <QColor>
#include <QImage>
#include <QPainter>

#include <cmath>
#include <string.h>

using namespace KIO;

static const quint32 stack_blur8_mul[255] = {
    512, 512, 456, 512, 328, 456, 335, 512, 405, 328, 271, 456, 388, 335, 292, 512, 454, 405, 364, 328, 298, 271, 496, 456, 420, 388, 360, 335, 312,
    292, 273, 512, 482, 454, 428, 405, 383, 364, 345, 328, 312, 298, 284, 271, 259, 496, 475, 456, 437, 420, 404, 388, 374, 360, 347, 335, 323, 312,
    302, 292, 282, 273, 265, 512, 497, 482, 468, 454, 441, 428, 417, 405, 394, 383, 373, 364, 354, 345, 337, 328, 320, 312, 305, 298, 291, 284, 278,
    271, 265, 259, 507, 496, 485, 475, 465, 456, 446, 437, 428, 420, 412, 404, 396, 388, 381, 374, 367, 360, 354, 347, 341, 335, 329, 323, 318, 312,
    307, 302, 297, 292, 287, 282, 278, 273, 269, 265, 261, 512, 505, 497, 489, 482, 475, 468, 461, 454, 447, 441, 435, 428, 422, 417, 411, 405, 399,
    394, 389, 383, 378, 373, 368, 364, 359, 354, 350, 345, 341, 337, 332, 328, 324, 320, 316, 312, 309, 305, 301, 298, 294, 291, 287, 284, 281, 278,
    274, 271, 268, 265, 262, 259, 257, 507, 501, 496, 491, 485, 480, 475, 470, 465, 460, 456, 451, 446, 442, 437, 433, 428, 424, 420, 416, 412, 408,
    404, 400, 396, 392, 388, 385, 381, 377, 374, 370, 367, 363, 360, 357, 354, 350, 347, 344, 341, 338, 335, 332, 329, 326, 323, 320, 318, 315, 312,
    310, 307, 304, 302, 299, 297, 294, 292, 289, 287, 285, 282, 280, 278, 275, 273, 271, 269, 267, 265, 263, 261, 259};

static const quint32 stack_blur8_shr[255] = {
    9,  11, 12, 13, 13, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 19,
    19, 19, 19, 19, 19, 19, 19, 19, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21,
    21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22,
    22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
    23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 24, 24, 24, 24,
    24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
    24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24};

inline static void blurHorizontal(QImage &image, unsigned int *stack, int div, int radius)
{
    quint32 *const pixels = reinterpret_cast<quint32 *>(image.bits());
    quint32 pixel = 0;

    const int width = image.width();
    const int height = image.height();
    const int wm = width - 1;

    const unsigned int mul_sum = stack_blur8_mul[radius];
    const unsigned int shr_sum = stack_blur8_shr[radius];

    for (int y = 0; y < height; y++) {
        unsigned int sum = 0;
        unsigned int sum_in = 0;
        unsigned int sum_out = 0;

        const int yw = y * width;
        pixel = pixels[yw];
        for (int i = 0; i <= radius; i++) {
            stack[i] = qAlpha(pixel);

            sum += stack[i] * (i + 1);
            sum_out += stack[i];
        }

        for (int i = 1; i <= radius; i++) {
            pixel = pixels[yw + qMin(i, wm)];

            unsigned int *stackpix = &stack[i + radius];
            *stackpix = qAlpha(pixel);

            sum += *stackpix * (radius + 1 - i);
            sum_in += *stackpix;
        }

        int stackindex = radius;
        for (int x = 0, i = yw; x < width; x++) {
            pixels[i++] = (((sum * mul_sum) >> shr_sum) << 24) & 0xff000000;

            sum -= sum_out;

            int stackstart = stackindex + div - radius;
            if (stackstart >= div) {
                stackstart -= div;
            }

            unsigned int *stackpix = &stack[stackstart];

            sum_out -= *stackpix;

            pixel = pixels[yw + qMin(x + radius + 1, wm)];

            *stackpix = qAlpha(pixel);

            sum_in += *stackpix;
            sum += sum_in;

            if (++stackindex >= div) {
                stackindex = 0;
            }

            stackpix = &stack[stackindex];

            sum_out += *stackpix;
            sum_in -= *stackpix;
        } // for (x = 0, ...)
    } // for (y = 0, ...)
}

inline static void blurVertical(QImage &image, unsigned int *stack, int div, int radius)
{
    int stackindex;
    int stackstart;

    quint32 *const pixels = reinterpret_cast<quint32 *>(image.bits());
    quint32 pixel;

    int w = image.width();
    int h = image.height();
    int hm = h - 1;

    int mul_sum = stack_blur8_mul[radius];
    int shr_sum = stack_blur8_shr[radius];

    unsigned int sum;
    unsigned int sum_in;
    unsigned int sum_out;

    for (int x = 0; x < w; x++) {
        sum = 0;
        sum_in = 0;
        sum_out = 0;

        pixel = pixels[x];
        for (int i = 0; i <= radius; i++) {
            stack[i] = qAlpha(pixel);

            sum += stack[i] * (i + 1);
            sum_out += stack[i];
        }

        for (int i = 1; i <= radius; i++) {
            pixel = pixels[qMin(i, hm) * w + x];

            unsigned int *stackpix = &stack[i + radius];
            *stackpix = qAlpha(pixel);

            sum += *stackpix * (radius + 1 - i);
            sum_in += *stackpix;
        }

        stackindex = radius;
        for (int y = 0, i = x; y < h; y++, i += w) {
            pixels[i] = (((sum * mul_sum) >> shr_sum) << 24) & 0xff000000;

            sum -= sum_out;

            stackstart = stackindex + div - radius;
            if (stackstart >= div) {
                stackstart -= div;
            }

            unsigned int *stackpix = &stack[stackstart];

            sum_out -= *stackpix;

            pixel = pixels[qMin(y + radius + 1, hm) * w + x];

            *stackpix = qAlpha(pixel);

            sum_in += *stackpix;
            sum += sum_in;

            if (++stackindex >= div) {
                stackindex = 0;
            }

            stackpix = &stack[stackindex];

            sum_out += *stackpix;
            sum_in -= *stackpix;
        } // for (y = 0, ...)
    } // for (x = 0, ...)
}

static void stackBlur(QImage &image, float radius)
{
    radius = qRound(radius);

    int div = int(radius * 2) + 1;
    unsigned int *stack = new unsigned int[div];

    blurHorizontal(image, stack, div, radius);
    blurVertical(image, stack, div, radius);

    delete[] stack;
}

void ImageFilter::shadowBlur(QImage &image, float radius, const QColor &color)
{
    if (radius < 0) {
        return;
    }

    if (radius > 0) {
        stackBlur(image, radius);
    }

    // Correct the color and opacity of the shadow
    QPainter p(&image);
    p.setCompositionMode(QPainter::CompositionMode_SourceIn);
    p.fillRect(image.rect(), color);
}
